Paraffin-embedded tissue is less accurate than frozen section analysis for determining VHL mutational status in sporadic renal cell carcinoma

INTRODUCTION

Literature controversies exist regarding the prognostic value of VHL mutations. The objective was to compare paraffin-embedded and frozen section specimens for VHL mutations detection and to evaluate the reliability of DNA analysis in formalin-fixed tissues.

METHODS

Seventy-six patients with clear cell renal cell carcinoma (RCC) previously assessed for VHL status from frozen samples were included. Seventy-three tumor samples were known to be mutated for VHL. DNA was extracted and an electrophoresis was performed to determine DNA quality. The whole coding sequence was synthesized by double PCR amplification followed by sequencing. Sequencing results were compared with those previously determined from frozen samples.

RESULTS

DNA could be extracted from the 76 paraffin samples. DNA quality was highly degraded and significantly less amplified by PCR in 34.2%, resulting in no sequence available for analysis in 57.7% and discordance with frozen samples in 42.3% of the cases respectively. VHL mutations were found in 52.1% of the whole paraffin samples whereas 98% were mutated; 72% could be sequenced, resulting in 69.1% of VHL mutations in this subset. Only half of observed mutations were fully consistent with frozen analysis in the 3 exons. Neomutations were found in 10.5% and 28.9% of known mutations in frozen samples were not detected in paraffin blocks. Only DNA quality significantly influenced PCR amplification and sequencing.

CONCLUSION

Tumoral DNA extraction and VHL mutation analysis can be performed from formalin-fixed paraffin-embedded (FFPE) tissue in RCC. But mutations identified tissues are not strictly concordant with those from frozen analysis and therefore results obtained from FFPE samples should be interpreted with care.

Loss of expression of TIMP3 in clear cell renal cell carcinoma

AIMS

In clear cell renal cell carcinoma (CCRCC), vascular endothelial growth factor (VEGF) represents the central positive mediator of tumour angiogenesis while VEGF receptor (VEGFR) is the primary target of anti-angiogenic therapies. TIMP3 is a physiological VEGFR-2 antagonist and thus could be considered as an anti-angiogenic factor. We therefore determined the status of this physiological inhibitor in CCRCC.

PATIENTS AND METHODS

Archival tumour from 105 patients was studied. TIMP3 expression was analysed using immuno-histochemistry and real-time RT-PCR. Results were correlated with clinicopathological variables. To analyse the mechanisms of gene silencing involved, we performed Multiplex Ligation-dependent Probe Amplification (MLPA) and methylation-specific MLPA (MS-MLPA). At last, we evaluated the main upstream pathway described implicating TGFbetaRII, which induces TIMP3 expression.

RESULTS

A down-expression of TIMP3, determined by immunohistochemistry, affected 100/105 renal cancers (95.2%). TIMP3 mRNA levels were significantly lower in high-grade tumours. Loss of heterozygosity of the TIMP3 gene was observed in 8 tumours (7.6%) and the 5'CpG island of the TIMP3 promoter was found to be methylated in 25 tumours (23.8%). A down-expression of TGFbetaRII was found in 85/105 CCRCCs (80.9%). A significant correlation was found between TIMP3 expression and TGFbetaRII expression.

CONCLUSIONS

This is the first demonstration that the loss of TIMP3 expression is observed in almost all CCRCCs. This loss of expression is a common molecular event in CCRCC. It may be an important initiation step for tumour development in a complex process implicating loss of heterozygosity on chromosome 22q, promoter hyper-methylation and inactivation of the TGFbetaRII pathway.

Absence of VHL gene alteration and high VEGF expression are associated with tumour aggressiveness and poor survival of renal-cell carcinoma

Background:

The von Hippel–Lindau gene (VHL) alteration, a common event in sporadic clear-cell renal-cell carcinoma (CCRCC), leads to highly vascularised tumours. Vascular endothelial growth factor (VEGF) is the major factor involved in angiogenesis, but the prognostic significance of both VHL inactivation and VEGF expression remain controversial. The aims of this study were to analyse the relationship between VHL genetic and epigenetic alterations, VHL expression and VEGF tumour or plasma expression, and to analyse their respective prognostic value in patients with CCRCC.

Methods:

A total of 102 patients with CCRCC were prospectively analysed. Alterations in VHL were determined by sequencing, Multiplex Ligation-dependent Probe Amplification (MLPA) and methylation-specific MLPA. Expression of pVHL and VEGF was determined by immunohistochemistry. Plasma VEGF was measured by enzyme-linked immunosorbent assay (ELISA).

Results:

VHL mutation, deletion and promoter methylation were identified in 70, 76 and 14 cases, respectively. Overall, at least one VHL-gene alteration occurred in 91 cases (89.2%). Both VEGF tumour and plasma expression appeared to be decreased in case of VHL alteration. Median progression-free survival and CCRCC-specific survival were significantly reduced in patients with wild-type VHL or altered VHL and high VEGF expression, which, therefore, represent two markers of tumour aggressiveness in CCRCC.

Conclusion:

Stratifying CCRCCs according to VHL and VEGF status may help tailor therapeutic strategy.

Low CAIX expression and absence of VHL gene mutation are associated with tumor aggressiveness and poor survival of clear cell renal cell carcinoma

We attempted to describe, in a series of clear cell renal cell carcinoma (RCC), the relationship between CAIX expression, VHL gene mutations, tumor characteristics and outcome. Radical nephrectomy was performed in 100 patients. Genomic DNA was extracted from frozen tumor samples. Four amplimers covering the whole coding sequence of the VHL gene were synthesized by PCR and sequenced. The monoclonal antibody M75 was used to evaluate CAIX protein expression immunohistochemically. VHL mutations were identified in 58 patients (58%) and high CAIX expression (>85%) was observed in 78 (78%). Tumors with VHL mutation showed higher CAIX expression than those without (p = 0.02). Low CAIX expression and absence of VHL mutation were associated with a more advanced tumors e.g., higher T stages and presence of metastases. VHL mutation and high CAIX expression predicted longer progression-free survival (p = 0.037) and disease-specific survival (p = 0.001), respectively. In combination, they defined three prognostic groups (p = 0.002): (i) good prognosis, defined as VHL mutation and high CAIX (2-year survival: 86%), (ii) intermediate prognosis with either VHL mutation or high CAIX (69%), and (iii) poor prognosis with no VHL mutation and low CAIX (45%, median survival 18 months). CAIX expression, but not VHL mutational status, was an independent prognostic factor in multivariate analysis. Taken together, CAIX expression and VHL mutational status are able to stratify patients with clear cell RCC into distinct groups with regards to clinicopathological variables and prognosis, with low CAIX expression and absence of VHL mutation being associated with a poor clinicopathological phenotype and diminished survival.

Update on the medical treatment of metastatic renal cell carcinoma

CONTEXT

Metastatic renal cell carcinoma (mRCC) has long been treated only by immunotherapy with good results only in a small population of patients. In recent years, major improvements in treatment possibilities have occurred with the advent of anti-angiogenic drugs. In the past 2 yr, pivotal phase III trials have confirmed this major breakthrough by increasing the progression-free survival rates and/or overall survival rates provided by sunitinib, sorafenib, and bevacizumab, and more recently by the mTOR (mammalian target of rapamycin) inhibitors temsirolimus and everolimus.

OBJECTIVE

To update the previous review on smart drugs published in the European Journal in 2006 (Patard JJ, et al. Understanding the importance of smart drugs in renal cell carcinoma. Eur Urol 2006; 49:633-43).

EVIDENCE ACQUISITION

Critical review of published literature 2006-2008 (Pubmed website search words: renal cell carcinoma and/or targeted therapy and prospective trials) and more recent meeting abstracts (American Society of Clinical Oncology 2007). Quality assessment included prospective phase I-III trials and critical evaluations with low numbers of patients, retrospective analyses, and slide presentations of meeting abstracts.

EVIDENCE SYNTHESIS

This review presents the current situation and provides more recent data on sequential treatment, the association of targeted drugs, and the treatment of non-clear-cell histologies.

CONCLUSIONS

Treatment of mRCC with targeted therapy centers on at least two major pathways: angiogenesis and mTOR involving inhibiting drugs that may be used alone, in combination, or sequentially.

Identification of pro-MMP-7 as a serum marker for renal cell carcinoma by use of proteomic analysis

BACKGROUND

No validated renal cell carcinoma (RCC) marker is known for detection of asymptomatic disease in selected populations or for prognostic purposes or treatment monitoring. We identified immunogenic proteins as tumor markers for RCC by combining conventional proteome analysis with serological screening, and we investigated the diagnostic clinical value of such markers in serum.

METHODS

We studied the immunogenic protein expression profile of CAL 54, a human RCC cell line, by 2-dimensional electrophoresis combined with immunoblotting using sera from healthy donors compared with RCC patients. We developed a homogeneous, fluorescent, dual-monoclonal immunoassay for metalloproteinase 7 (MMP-7) and used it to measure MMP-7 in sera from 30 healthy donors, 30 RCC patients, and 40 control patients.

RESULTS

Pro-MMP-7 (29 kDa; pI 7.7) in the CAL 54 cell line secretome was an immunogenic protein reactive with RCC patient sera but not with control sera. The concentrations of pro-MMP-7 were increased (P <0.0001) in sera of RCC patients (median 7.56 microg/L; range 3.12-30.5 microg/L) compared with healthy controls (median 2.13 microg/L; range 0.17-3.5 microg/L). Serum pro-MMP-7 had a sensitivity of 93% (95% CI 78%-99%) at a specificity of 75% (59%-87%) for RCC in the samples tested.

CONCLUSION

Proteomics technology combined with serology led to the identification of serum pro-MMP-7 as a marker of RCC and represents a powerful tool in searching for candidate proteins as biomarkers.

Plasma level and tissue expression of vascular endothelial growth factor in renal cell carcinoma: a prospective study of 50 cases

Vascular endothelial growth factor (VEGF) is the major factor involved in angiogenesis. Although it is known that one of the functions of VEGF is to regulate neovascularization in renal cell carcinomas, the relationship between the production of VEGF in tumor tissue and its concentration in blood has not yet been studied. The aims of this study were to determine, in a series of conventional renal cell carcinoma (CRCC) cases, (1) VEGF expression and VEGF pattern in tumor cells, (2) the relationship between VEGF expression/pattern and VEGF levels in plasma (pVEGF), and (3) the association with usual clinical and pathologic prognostic factors. Fifty patients operated on for CRCC by radical nephrectomy were included. Clinical and histologic parameters were studied. VEGF expression and VEGF pattern in tumor cells was immunohistochemically recorded. pVEGF levels and platelet count were analyzed in relation to clinical and histologic parameters. Intratumoral VEGF expression associated with a cytoplasmic VEGF pattern was significantly higher in patients with high pVEGF levels (P = .01). Both VEGF expression and pVEGF levels were significantly correlated with Fuhrman grade (P = .002 and P = .01, respectively) and tumor stage (P = .006 and P = .008, respectively). In addition, VEGF expression was also correlated with tumor necrosis (P = .001) and progression (P = .001). We demonstrated that in CRCC with tumor necrosis, VEGF expression, pVEGF levels, and platelet count were significantly higher than in CRCC with no tumor necrosis (P = .001, P = .03, and P = .001, respectively). Our results revealed that cytoplasmic VEGF expression and pVEGF levels are associated with usual prognostic factors and progression in CRCC, which may allow VEGF to be used as a prognostic marker for CRCC, especially in patients with VEGF-targeted therapy.

Use of carbonic anhydrase IX (CAIX) expression and Von Hippel Lindau (VHL) gene mutation status to predict survival in renal cell carcinoma

5042

Background: VHL gene mutations induce the expression of CAIX, and previous studies have shown that low CAIX results in worse prognosis for RCC. We attempt to further describe the relationship between CAIX expression, VHL gene mutations and tumor characteristics. Methods: Radical nephrectomy was performed in 100 patients at 2 centers. Genomic DNA was extracted from frozen tumor samples using the QIAmp DNA mini kit. Four amplimers covering the whole coding sequence of the VHL gene were synthesized by PCR and sequenced by Big Dye. Mutation bearing sequences were confirmed by a second round of sequencing. The monoclonal antibody M75 was used to score the expression of the CAIX protein. Life table, Kaplan-Meier and Cox regression analyses addressed RCC-specific mortality (RCC-SM). Results: VHL mutations were identified in 58 patients (58%) and CAIX tumor expression ranged from 0% to 100%. Low CAIX expression (<85%) was associated with absence of VHL mutation (p=0.02), larger tumors (p=0.002), higher T stage (p=0.007), nodal metastases (p=0.001) and higher Fuhrman grade (p=0.006). Absence of VHL mutation was associated with worse ECOG (p=0.005), higher T stage (p=0.01) and presence of nodal (p=0.03) and distant metastases (p=0.02). Categorically-coded, CAIX was a statistically significant predictor of RCC-SM (p=0.002), while VHL mutation approached statistical significance (p=0.08) and a trend was observed for worse survival when VHL was not mutated. Patients with both high CAIX and VHL mutation had better survival (95.9% 1 year and 6 year median survival) than their counterparts with low CAIX expression and absence of VHL mutation (62.9% 1 year and 1.5 year median survival) (p<0.001). In Cox regression analyses, neither CAIX (p=0.06) nor VHL (p=0.4) achieved independent predictor status, when adjusted for age, gender, TNM stage, tumor size, Fuhrman and ECOG. Conclusions: Low CAIX expression is associated with the absence of VHL mutation and aggressive tumor characteristics, and is a statistically significant predictor of poor prognosis in patients with clear cell RCC.

No significant financial relationships to disclose.

Interleukin-6 and vascular endothelial growth factor release by renal cell carcinoma cells impedes lymphocyte-dendritic cell cross-talk

Anti-tumour T cell response requires antigen presentation via efficient immunological synapse between antigen presenting cells, e.g. dendritic cells (DC), and specific T cells in an adapted Th1 cytokine context. Nine renal cell carcinoma (RCC) primary culture cells were used as sources of tumour antigens which were loaded on DC (DC-Tu) for autologous T cell activation assays. Cytotoxic activity of lymphocytes stimulated with DC-Tu was evaluated against autologous tumour cells. Assays were performed with 75 grays irradiated tumour cells (Tu irr) and with hydrogen peroxide +/- heat shock (Tu H(2)O(2) +/- HS) treated cells. DC-Tu irr failed to enhance cytotoxic activity of autologous lymphocytes in seven of 13 assays. In all these defective assays, irradiated tumour cells displayed high interleukin (IL)-6 and vascular endothelial growth factor (VEGF) release. Conversely, when tumour cells released low IL-6 levels (n = 4), DC-Tu irr efficiently enhanced CTL activity. When assays were performed with the same RCC cells treated with H(2)O(2) + HS, DC-Tu stimulation resulted in improved CTL activity. H(2)O(2) + HS treatment induced post-apoptotic cell necrosis of tumour cells, totally abrogated their cytokine release [IL-6, VEGF, transforming growth factor (TGF)-beta1] and induced HSP70 expression. Taken together, data show that reduction in IL-6 and VEGF release in the environment of the tumour concomitantly to tumour cell HSP expression favours induction of a stronger anti-tumour CTL response.

Differential expression of genes related to HFE and iron status in mouse duodenal epithelium

Iron absorption, distribution, use, and storage are thought to be tightly regulated since altered iron stores may lead to cellular damage and disease. HFE, the hereditary hemochromatosis gene product, is expressed in the crypts of the duodenum, but the molecular mechanism by which it contributes to the inhibition of iron absorption is still unknown. In this study we aimed to identify transcriptional profiles in the duodenal epithelium of Hfe(-/-) mice. We used dedicated microarrays to compare gene expression among the duodenum of Hfe(-/-) mice, induced iron overload mice, and control mice. We found 151 differentially expressed genes and unknown sequences between Hfe(-/-) mice and normal littermates. Gene profiling revealed a gene subset more specific for Hfe inactivation. The functional annotation of upregulated genes highlighted that mucus production and cell maintenance may account for the influence of Hfe on epithelium integrity and luminal iron uptake.

Biological significance of serum VEGF measurement in renal cell carcinoma

4596

Background: VEGF plays an important role in Renal Cell Carcinoma (RCC) tumor angiogenesis and is a relevant molecular target. Our objective was to correlate serum VEGF measurement to clinical, biological and pathological variables in renal tumors. Methods: 206 patients who were operated for a renal tumor at our institution were prospectively assessed for serum VEGF measurement (enzyme-linked immunosorbent assay, R&D systems). Informed consent was obtained in all cases. Symptoms at presentation, pre-operative biology (haemoglobin, WBC count, platelet count, serum creatinin, calcemia, CRP, ASAT, ALAT, gamma-glutamyltransferase (γGT), Alkaline Phosphatases), TNM stage, Fuhrman grade and final pathology (benign vs malignant histology, histologic subtype) were systematically recorded. Qualitative and quantitative variables were compared by using Chi-square (Fischer exact test) and Student t tests, respectively. Results: There were 128 males (62.1%) and 78 females (37.9%). 185 tumors were malignant at histology (89.8%) including 155 tumors with clear cell histology (83.8%). Median serum VEGF level was 361 ng/ml (41–3090). Mean serum VEGF was not significantly different between benign and malignant tumors as well as between clear cell and non clear cell carcinomas (p: 0.4 and 0.8 respectively). Serum VEGF was strongly associated with symptoms, T Stage (p: 0.0001), N Stage (p: 0.004), Fuhrman grade (p: 0.007) and tumor necrosis (p: 0.004) but not with M Stage (p: 0.3). Serum VEGF was also found to be strongly associated with: haemoglobin, CRP, platelet count (p: 0.0001) and Alkaline phosphatases (p: 0.001). A weaker association was found between serum VEGF and γGT, ASAT (p: 0.05) or ALAT (p: 0.09). Finally serum VEGF was associated with cancer specific survival (p: 0.01). Conclusion: Serum VEGF is strongly associated with most usual clinical, biological and pathological prognostic parameters in RCC. Serum VEGF measurement should be further evaluated for prognostic purpose as well as for treatment monitoring.

No significant financial relationships to disclose.

Pilot study of VHL mutation analysis to predict response to interleukin-2 in patients with metastatic renal cell carcinoma

14539

Background: More than 300 different mutations have been described in von Hippel-Lindau (VHL) families and nearly 100 in sporadic RCC. In familial cases, there is an excess of mutations in exon 3 and exon 1, whereas mutations are evenly distributed in sporadic cases. Recent evidence suggests the importance of genotype/phenotype correlations with different VHL gene mutations contributing to a tumor’s unique biological behavior. We performed a pilot study to compare the incidence and type of VHL mutation in IL-2 complete responders (CR) and non-responders (NR). Methods: Genomic DNA was extracted from 20 frozen clear cell tumour samples (10 CR and 10 NR) using Qiamp DNA mini kits (Qiagen). Four amplimers covering the entire coding sequence and three exon/intron junctions of the VHL gene were synthesized by PCR. PCR products were subsequently purified and were sequenced using Big Dye Primer Cycle Sequencing kit (Perkin-Elmer Applied Biosystems) and an automated DNA sequencer (Perkin-Elmer Applied Biosystems). Point mutation detection was performed on DNA sequencing gels from colored peak chromatograms. Mutation bearing sequences were confirmed by a second round of PCR and sequencing. Results: In the CR patients, only 2 out of 10 samples (20%) had evidence of a VHL mutation. These VHL mutations included a false sense mutations in exon 2, comprised of a C to T transition at position 646 in the cDNA, creating a stop codon, and a frameshift mutation in exon 1 introducing in one allele an abnormal stop codon at the beginning of exon 3 potentially leading to a shorter protein product. In the 10 non-responder samples, there was also a 2 out of 10 (20%) incidence of VHL mutations. These mutations included a complex 12 nucleotide deletion in the third exon in the a domain of the protein, and a G deletion in the first exon introducing a premature stop codon. Conclusions: In this small pilot study of metastatic RCC patients, there were relatively few VHL gene mutations, and VHL mutations did not appear to correlate with response to IL-2 therapy. This study, however, does not assess inactivation of VHL genes due to hypermethylation. An expanded genetic profile to evaluate IL-2 responders versus non-responders using 500k SNP Chips is underway.

No significant financial relationships to disclose.

Relationship between VHL mutation status, tumor VEGF expression and plasma VEGF measurement in sporadic renal cell carcinoma

4602

Background: The relationship between VHL mutation status and prognosis in renal cell carcinoma (RCC) remains controversial. The aim of this study was to evaluate prospectively the association between VHL status, tumor VEGF expression, plasma VEGF levels and usual prognostic parameters in RCC. Methods: 70 patients with clear cell RCCs were included in this study. Genomic DNA was extracted using the QIAmp DNA mini kit (Qiagen) from frozen tumor samples. Four amplimers covering the whole coding sequence and exon/intron junctions of the VHL gene were synthetized by PCR followed by Big Dye sequencing (Applied Biosystems). Mutation bearing sequences were confirmed in a second round of PCR and sequencing reactions. Tumor VEGF expression was determined by immunohistochemistry and plasma VEGF was measured by enzyme-linked immunosorbent assay (Quantikine immunoassay, R&D systems). Results were expressed in pg/ml. Qualitative and quantitative variables were compared by using Chi-square (Fischer exact test) and Student t tests, respectively. Results: A VHL mutation was found in 46 cases (65.7%). VHL mutations were localized in exon 1, 2 and 3 in 23, 16 and 7 cases respectively. Median tumor VEGF expression was 45% (5–100). Median plasma VEGF was 104 pg/ml (13–1430). A significant association was found between VHL mutation and N stage (p: 0.01), Fuhrman grade, symptoms at presentation (p: 0.02) or tumor size (p: 0.007). A VHL mutation was found in 83.5% of low grade (G1–2) and 80% of incidental tumors respectively. A trend towards more frequent VHL mutations was observed in T1 tumors (87% mutation rate, p: 0.07) and in good performance status patients. Interestingly, VEGF tumor expression and plasma VEGF levels were not significantly different among patients with tumors having or not mutated VHL (p: 0.7). Conclusion: VHL mutations are more frequent in small incidental low stage or low grade tumors. Although VHL inactivation was not specifically determined in this study, we failed to show any association between VHL mutational status and VEGF tumor or plasma expression suggesting that other pathways than the VHL/HIF axis are required for explaining the angiogenic phenotype of RCC.

No significant financial relationships to disclose.

Iron-related transcriptomic variations in CaCo-2 cells, an in vitro model of intestinal absorptive cells

Regulation of iron absorption by duodenal enterocytes is essential for the maintenance of homeostasis by preventing iron deficiency or overload. Despite the identification of a number of genes implicated in iron absorption and its regulation, it is likely that further factors remain to be identified. For that purpose, we used a global transcriptomic approach, using the CaCo-2 cell line as an in vitro model of intestinal absorptive cells. Pangenomic screening for variations in gene expression correlating with intracellular iron content allowed us to identify 171 genes. One hundred nine of these genes are clustered into five types of expression profile. This is the first time that most of these genes have been associated with iron metabolism. Functional annotation of these five clusters indicates potential links between the immune response, proteolysis processes, and iron depletion. In contrast, iron overload is associated with cellular metabolism, especially that of lipids and glutathione involving redox function and electron transfer.